As device dimensions are decreasing in the microelectronics industry, selective deposition of metals is becoming critically important. Previous approaches for selective deposition include intrinsic differences in nucleation rates, sacrificial solid state layers, activation of the growth surface, and passivation of the non-growth surface, e.g., by use of a SAM (self-assembled monolayer).
Compared to other metals, Cu is more difficult to pattern because of the lack of an effective etchant. Quite often, even if selective growth is achieved by a selective process, stray nucleation on the non-growth surface still occurs. Such nuclei keep on growing during the deposition and eventually cause a reliability problem and device failure. Ideally, stray nucleation needs to be completely eliminated, or if nuclei happen to form their growth rate needs to be decreased to a very small value to keep the coverage of Cu minimal on the non-growth surface.
Disclosures relating to the deposition of smooth films include: Babar et al., “Chemical Vapor Deposition of Copper: Use of a Molecular Inhibitor to Afford Uniform Nanoislands or Smooth Films,” ECS J. Solid State Sci. and Tech. 3(5) Q79-Q83 (2014); Babar et al., “Growth Inhibitor To Homogenize Nucleation and Obtain Smooth HfB2 Thin Films by Chemical Vapor Deposition,” Chem. Mater. 25, 662-667 (2013); Hampden-Smith and Kodas, “Chemical Vapor Deposition of Metals: Part 2. Overview of Selective CVD of Metals,” Chem. Vap. Deposition 1(2), 39-48 (1995); Jain et al., “Control of Selectivity During Chemical Vapor Deposition of Copper From Copper (I) Compounds Via Silicon Dioxide Surface Modification,” App. Phys. Lett. 61, 2662-2664 (1992); and Dubois and Zegarski, “Selectivity and Copper Chemical Vapor Deposition,” J. Electrochem. Soc. 139(11), 3295-3299 (1992).
It will be appreciated from the foregoing that there is currently a need in the art for methods to selectively grow metal films, such as copper films. In addition, methods are needed to control morphology during the growth of metal films on challenging substrates, such as oxides.